diff --git a/src/main.rs b/src/main.rs
index 4b1040f..078e35b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,35 +1,84 @@
-use crate::list::{ListNode, make_list};
+use crate::arr::make_matrix;
+use std::cmp::Reverse;
+use std::collections::BTreeMap;
 
 mod arr;
 mod list;
 mod tree;
 
-struct Solution {}
+struct MinStack {
+    heap: BTreeMap<Reverse<i32>, i32>,
+    stack: Vec<i32>,
+}
 
-use crate::tree::{TreeNode, build_tree_from_str};
-use std::cell::RefCell;
-use std::rc::Rc;
-
-impl Solution {
-    pub fn sum_numbers(root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
-        Self::dfs(root).iter().map(|x| x.parse::<i32>().unwrap()).sum()
+/**
+ * `&self` means the method takes an immutable reference.
+ * If you need a mutable reference, change it to `&mut self` instead.
+ */
+impl MinStack {
+    fn new() -> Self {
+        MinStack {
+            heap: BTreeMap::new(),
+            stack: Vec::new(),
+        }
     }
-    pub fn dfs(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<String> {
-        if root.is_none() {
-            return vec![];
+
+    fn push(&mut self, value: i32) {
+        self.stack.push(value);
+        let entry = self.heap.entry(Reverse(value)).or_insert(0);
+        *entry += 1;
+    }
+
+    fn pop(&mut self) {
+        let ele = self.stack.pop();
+        let entry = self.heap.get_mut(&Reverse(ele.unwrap())).unwrap();
+        if *entry == 1 {
+            self.heap.remove_entry(&Reverse(ele.unwrap()));
+        } else {
+            *entry -= 1;
         }
-        let x = root.as_ref().unwrap();
-        let mut arr = Self::dfs(Rc::clone(x).borrow().left.clone());
-        arr.append(&mut Self::dfs(Rc::clone(x).borrow().right.clone()));
-        if arr.is_empty() {
-            return vec![x.borrow().val.to_string()];
-        }
-        arr.iter().map(|y| x.borrow().val.to_string() + y).collect()
+    }
+
+    fn top(&self) -> i32 {
+        self.stack.last().cloned().unwrap()
+    }
+
+    fn get_min(&self) -> i32 {
+        self.heap.last_key_value().unwrap().0.0
     }
 }
+
+/**
+ * Your MinStack object will be instantiated and called as such:
+ * let obj = MinStack::new();
+ * obj.push(value);
+ * obj.pop();
+ * let ret_3: i32 = obj.top();
+ * let ret_4: i32 = obj.get_min();
+ */
 fn main() {
-    println!(
-        "{:?}",
-        Solution::sum_numbers(build_tree_from_str("[4,9,0,5,1]"))
-    );
+    let opers = [
+        "MinStack", "push", "push", "push", "getMin", "pop", "getMin", "pop", "getMin", "pop",
+        "push", "push", "push", "getMin", "pop", "top", "getMin", "pop", "getMin", "pop",
+    ];
+    let data =
+        make_matrix("[[],[0],[1],[0],[],[],[],[],[],[],[-2],[-1],[-2],[],[],[],[],[],[],[]]");
+    let mut st = MinStack::new();
+    for i in 1..opers.len() {
+        match opers[i] {
+            "push" => {
+                st.push(data[i][0]);
+            }
+            "pop" => {
+                st.pop();
+            }
+            "top" => {
+                println!("{:?}", st.top());
+            }
+            "getMin" => {
+                println!("{:?}", st.get_min());
+            }
+            _ => {}
+        }
+    }
 }